Hydraulic fracturing is used in the recovery of hydrocarbons from subterranean formations to fracture the formation and provide flow channels. These flow channels facilitate movement of the hydrocarbons to the wellbore so that the hydrocarbons may be pumped from the well.
In hydraulic fracturing operations, a fracturing fluid is hydraulically injected into a wellbore penetrating the subterranean formation and is forced against the formation strata at a pressure sufficient to crack and fracture the strata.
The fracturing fluids are typically thickened or gelled aqueous compositions that also carry a proppant, which, when placed in the fracture by movement of the fracturing fluid containing proppant into the crack in the rock, “props” the fracture open, thereby providing improved flow of the hydrocarbon into the wellbore.
There has been considerable interest in using viscoelastic surfactants to increase the viscosity or induce gel formation in aqueous fracturing fluids. See, for example, U.S. Pat. Nos. 4,695,389, 4,725,372, 4,800,036, 5,551,516, 5,964,295, 5,979,557, 6,258,859, 6,306,800, 6,412,561, 6,435,277, 6,506,710 and PCT/US00/24142. It is believed that the viscoelastic surfactants form micelles that are able to viscosify the fluid and carry the proppant into the fractured rock. As oil is produced, it breaks the micelle, allowing the surfactants to be removed.
A viscoelastic surfactant composition comprising erucyl methyl bis(2-hydroxyethyl) ammonium chloride and a polymer and use of the composition in subterranean formations is disclosed in published U.S. Patent Application No. 20030134751.
There is, nonetheless, an ongoing need to develop new viscoelastic surfactant fracturing fluid compositions, particularly compositions having higher viscosity performance at low temperature and improved high temperature performance relative to existing technology, thereby allowing for the use of lower surfactant concentrations as well as enhanced ability to carry sand.